Mission Teams Prepare for Critical Days

From its initial leap off the pad at 17:57 UTC (18:57 CET) until the satellite separates from the Breeze upper stage high in space, the journey will take just 80 minutes, with Sentinel-3A injected into a polar orbit at about 815 km altitude, orbiting 40 times faster than an aircraft.

At ESOC, ESA’s mission control centre in Darmstadt, Germany, a team of highly trained specialists will be watching closely, waiting for Sentinel-3A to complete an initial automated sequence and start transmitting a signal via the Agency’s Kiruna ground station in Sweden.

“After separation from the Breeze upper stage, we have to wait about 13 minutes for first ‘acquisition of signal’ over Kiruna, while our satellite uses its sensors and actuators to stabilise towards a Sun-pointing attitude,” says Spacecraft Operations Manager José Morales.

“At that point, we expect to establish stable communication with our ‘new-born baby’, enabling us to verify its health and status, assume command and start the complex process of bringing it into a stable Earth-pointing mode.”

Mission controllers will be very anxious to verify that the power-producing solar arrays have automatically deployed, as the onboard batteries will only last five to six hours.

“The first 36 hours will be the most intensive,” says José.

Receipt of the radio signals from space will mark the start of an extremely busy three-day period for José and his colleagues, who will work round the clock to operate the spacecraft through the critical LEOP – the launch and early orbit phase – for which the Mission Control Team has trained for months.

Training for LEOP involved multiple teams of engineers and scientists at ESOC totalling about 50 people, including spacecraft engineers, specialists working on tracking stations and the sophisticated ‘ground segment’ – the hardware and software used to control the satellite and distribute its data – and experts working in flight dynamics, software and networks, as well as simulation and training teams.

The simulation training campaign followed several years of preparation at the ESOC centre, during which engineers developed flight procedures, built up the ground systems that will control the satellite and tested hardware and software using live data connections to the actual satellite as it was being built and assembled.

For launch, the team at ESOC includes representatives from ESA’s Sentinel project team, as well as several operations engineers integrated within the Flight Control Team and shared with Eumetsat, the European organisation for the exploitation of meteorological satellites.

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